Process for producing dihydroxydiphenylsulfone

ABSTRACT

The present invention provides a process for producing dihydroxydiphenylsulfone wherein trihydroxytriphenylsulfone and coloring impurities are effectively removed without altering the isomeric composition of dihydroxydiphenylsulfone. In particular, the present invention provides a process for producing dihydroxydiphenylsulfone comprising the steps of dissolveing or suspending in an aqueous solvent crude dihydroxydiphenylsulfone containing trihydroxytriphenylsulfone, adjusting the pH to 5–7, optionally cooling, and separating the crystalline dihydroxydiphenylsulfone thus precipitated.

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application PCT/JP03/05228, filed Apr. 24, 2003, whichclaims priority to Japanese Patent Application No. 2002-123646, filedApr. 25, 2002. The International Application was not published under PCTArticle 21(2) in English.

TECHNICAL FIELD

The present invention relates to a process for producingdihydroxydiphenylsulfone.

BACKGROUND OF THE INVENTION

4,4′-Dihydroxydiphenylsulfone (hereinafter occasionally referred to as4,4′-DDS), 2,4′-dihydroxydiphenylsulfone (hereinafter occasionallyreferred to as 2,4′-DDS) and mixtures thereof are of use as materialsfor engineering polymers, color developers for heat-sensitive paper, andthe like. Trihydroxytriphenyldisulfone (hereinafter occasionallyreferred to as TTDS) and coloring impurities generated during thereactions for producing dihydroxydiphenylsulfone cause the properties ofdihydroxydiphenylsulfone to be impaired. Therefore, a process for theeffective removal thereof has been sought.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a process for producingdihydroxydiphenylsulfone wherein TTDS and coloring impurities areeffectively removed without altering the isomeric composition ofdihydroxydiphenylsulfone.

The present invention provides processes for producingdihydroxydiphenylsulfone as presented below:

-   Item 1. A process for producing dihydroxydiphenylsulfone comprising    the steps of:    -   dissolving or suspending crude dihydroxydiphenylsulfone        containing trihydroxytriphenylsulfone in an aqueous solvent;    -   adjusting the pH of the aqueous solvent to 5–7;    -   optionally cooling the aqueous solvent; and    -   separating the precipitated crystalline        dihydroxydiphenylsulfone.-   Item 2. A process for producing dihydroxydiphenylsulfone comprising    the steps of:    -   dissolving or suspending crude dihydroxydiphenylsulfone        containing trihydroxytriphenylsulfone in an aqueous solvent by        adding alkali;    -   adjusting the pH of the aqueous solvent to 5–7 by adding an        acidic substance;    -   optionally cooling the aqueous solvent; and    -   separating the precipitated crystalline        dihydroxydiphenylsulfone.-   Item 3. The process for producing dihydroxydiphenylsulfone according    to Item 1 or 2, wherein the pH is adjusted to 6 or greater and less    than 7.-   Item 4. The process for producing dihydroxydiphenylsulfone according    to any one of Items 1–3, wherein the crude dihydroxydiphenylsulfone    contains trihydroxytriphenylsulfone in a proportion of 30 wt. % or    less.-   Item 5. The process for producing dihydroxydiphenylsulfone according    to any one of Items 1–4, wherein the crystalline    dihydroxydiphenylsulfone is separated at 60° C. or lower.

It is essential to the present invention to adjust the pH of the aqueoussolvent in which TTDS-containing crude dihydroxydiphenylsulfone isdissolved or suspended to 5–7. Thus, pH adjustment is not particularlynecessary if, for example, the aforementioned pH range is satisfiedmerely by introducing TTDS-containing crude dihydroxydiphenylsulfoneinto an aqueous solvent. The scope of the invention includes such anembodiment.

The starting material of the present invention, i.e., TTDS-containingcrude dihydroxydiphenylsulfone, is not limited, and usable aresolvent-containing dihydroxydiphenylsulfone reaction products, such areaction product dried to remove solvent, such a reaction product fromwhich sulfonic acids have been removed, a solution prepared by theaddition of a basic aqueous solution to such a reaction product and theextraction of dihydroxydiphenylsulfone isomers therefrom, a commerciallyavailable crude product containing an isomeric mixture, etc.

The crude dihydroxydiphenylsulfone preferably contains TTDS in aproportion of 30 wt. % or less, and more preferably 20 wt. % or less.The weight ratio of 2,4′-DDS to 4,4′-DDS in the crudedihydroxydiphenylsulfone is not limited, and it is preferably2,4′-DDS/4,4′-DDS=0/100 to 99/1, and more preferably 0.1/99.9 to 98/2.

Moreover, crude dihydroxydiphenylsulfone usable herein may contain otherimpurities such as sulfonic acids, reaction solvents, etc.

Water is preferable as the aqueous solvent used in the presentinvention. Water may contain a water-miscible solvent in a proportion of40 wt. % or less, such as methanol, ethanol, isopropyl alcohol or likeC₁₋₃ alcohol; acetone, methyl ethyl ketone or like ketone; ethyleneglycol, diethylene glycol or like polyhydric alcohol; etc.

The amount of aqueous solvent to be used is preferably at most 20 timesthe weight of crude dihydroxydiphenylsulfone, preferably 0.5–10 timesand particularly preferably 2–8 times.

Examples of alkalis usable in the present invention include LiOH, NaOH,KOH and like alkali metal hydroxides; Li₂CO₃, Na₂CO₃, K₂CO₃ and likealkali metal carbonates; LiHCO₃, NaHCO₃, KHCO₃ and like alkali metalbicarbonates; ammonia, triethylamine and like amine compounds; etc.Among these examples, alkali metal hydroxides are preferable, and NaOHis particularly preferable.

The amount of alkali to be used is preferably 2 equivalents or lessrelative to the total amount of 2,4′-DDS, 4,4′-DDS and TTDS, and morepreferably 0.001–1 equivalents. The term “1 equivalent” herein refers tothe amount of alkali necessary to convert 1 mol of 2,4′-DDS, 4,4′-DDSand TTDS in total to 1 mol of a mono alkali metal salt of 2,4′-DDS,4,4′-DDS and TTDS. Therefore, when an alkali metal hydroxide, alkalimetal bicarbonate or an amine compound is used as an alkali, the molaramount thereof is preferably no greater than twice the molar amount of2,4′-DDS, 4,4′-DDS and TTDS contained in crude dihydroxydiphenylsulfone,and more preferably 0.001 times to equimolar. Moreover, when used as analkali, an alkali metal carbonate is preferably used in no greater thanequimolar relative to the molar amount of 2,4′-DDS, 4,4′-DDS and TTDScontained in crude dihydroxydiphenylsulfone, and more preferably0.0005–0.5 times.

When crude dihydroxydiphenylsulfone contains sulfonic acids, it ispreferable to add alkali in an amount sufficient to neutralize thesulfonic acids in addition to the amount described above.

The temperature for dissolving or suspending crudedihydroxydiphenylsulfone after adding alkali is preferably within therange of from room temperature to the boiling temperature of thesolvent. Dissolution and suspension may be carried out under pressure,if necessary. Moreover, if necessary, the dissolved crudedihydroxydiphenylsulfone may be treated with activated carbon, and areducing agent may be added to decolorize.

Subsequently, an acidic substance is added to the solution or suspensionof crude dihydroxydiphenylsulfone. Examples of acidic substances includesulfuric acid, hydrochloric acid, nitric acid, phosphoric acid and likemineral acids, acetic acid and like organic acids, etc.

Once the solution or suspension is mixed with an acidic substance and,if necessary, cooled, a dihydroxydiphenylsulfone isomeric mixturecomposed of 2,4′-DDS and 4,4′-DDS precipitates. The pH of the solutionor suspension in this instance is 5–7, preferably 6 or greater and lessthan 7, and more preferably 6.2–6.8. The precipitation temperature ispreferably within the range of from room temperature to 90° C.

The precipitated crystalline dihydroxydiphenylsulfone isomeric mixturecan be separated according to conventional solid-liquid separationtechniques such as filtration (vacuum filtration, pressure filtration,centrifugation, etc.), decantation, etc. The temperature upon separatingthe crystals is preferably 60° C. or lower, more preferably 50° C. orlower, and particularly preferably 20–45° C.

The dihydroxydiphenylsulfone obtained according to the productionprocess of the invention as described above contains TTDS in aproportion of 3 wt. % or less, more preferably 1 wt. % or less, andparticularly preferably 0.2 wt. % or less.

Moreover, according to the production process of the invention, coloringimpurities contained in crude dihydroxydiphenylsulfone can be highlyeffectively removed. For example, when the production process of thepresent invention is performed using crude dihydroxydiphenylsulfonehaving an APHA value of 1000–2000 in 5% acetone solution, the APHA valueof the resulting dihydroxydiphenylsulfone is decreased to about 500 orless.

BEST MODE FOR CARRYING OUT THE INVENTION

Examples are given below to illustrate the process of the invention inmore detail, but the scope of the invention is not limited to theseexamples.

EXAMPLE 1

To 100 g of crude dihydroxydiphenylsulfone isomeric mixture (APHA valueof 1000 in 5% acetone solution) containing 75 wt. % 4,4′-DDS, 20 wt. %2,4′-DDS and 5 wt. % TTDS (4,4′-DDS, 2,4′-DDS and TTDS totaling 0.39mol) were added 300 g of water and 8 g of sodium hydroxide (0.2 mol; 0.5times the total molar amount of 4,4′-DDS, 2,4′-DDS and TTDS), and heatedto 90° C. to dissolve the isomeric mixture. The solution was mixed with50% sulfuric acid at 50° C. to adjust the pH to 6.5. The solution wascooled to 35° C., and the crystals thus precipitated were filtered off,washed with water and dried, thereby giving 92 g of dried crystals. AnHPLC analysis showed 78.9 wt. % 4,4′-DDS, 21.0 wt. % 2,4′-DDS and 0.1wt. % TTDS. A 5% acetone solution thereof had an APHA value of 400.

EXAMPLE 2

The procedure described in Example 1 was repeated except for using 100 gof crude dihydroxydiphenylsulfone isomeric mixture (APHA value of 1500in 5% acetone solution) containing 50 wt. % 4,4′-DDS, 40 wt. % 2,4′-DDSand 10 wt. % TTDS (4,4′-DDS, 2,4′-DDS and TTDS totaling 0.38 mol),thereby giving 89 g of dried crystals. An HPLC analysis showed 55.8 wt.% 4,4′-DDS, 44.0 wt. % 2,4′-DDS and 0.2 wt. % TTDS. A 5% acetonesolution thereof had an APHA value of 500.

EXAMPLE 3

The procedure described in Example 1 was repeated except for using 100 gof crude dihydroxydiphenylsulfone isomeric mixture (APHA value of 1000in 5% acetone solution) containing 95 wt. % 4,4′-DDS, 2 wt. % 2,4′-DDSand 3 wt. % TTDS (4,4′-DDS, 2,4′-DDS and TTDS totaling 0.40 mol),thereby giving 95 g of dried crystals. An HPLC analysis showed 98 wt. %4,4′-DDS, 2 wt. % 2,4′-DDS and 0 wt. % TTDS. A 5% acetone solutionthereof had an APHA value of 400.

EXAMPLE 4

To 100 g of crude dihydroxydiphenylsulfone isomeric mixture (APHA valueof 1000 in 5% acetone solution) containing 69 wt. % 4,4′-DDS, 19 wt. %2,4′-DDS and 12 wt. % TTDS (4,4′-DDS, 2,4′-DDS and TTDS totaling 0.38mol) were added a mixed solution of 40 ml methanol and 360 ml water and4.8 g of sodium hydroxide (0.12 mol; 0.3 times the total molar amount of4,4′-DDS, 2,4′-DDS and TTDS), and heated to 80° C. to dissolve theisomeric mixture. The solution was mixed with sulfuric acid at 50° C. toadjust the pH to 6.7. The solution was cooled to 25° C., and thecrystals thus precipitated were filtered off, washed with water anddried, thereby giving 80 g of dried crystals. An HPLC analysis showed 78wt. % 4,4′-DDS, 22 wt. % 2,4′-DDS and 0 wt. % TTDS. A 5% acetonesolution thereof had an APHA value of 300.

EXAMPLE 5

The procedure described in Example 1 was repeated except for using 100 gof crude dihydroxydiphenylsulfone isomeric mixture (APHA value of 1000in 5% acetone solution) containing 17 wt. % 4,4′-DDS, 78 wt. % 2,4′-DDSand 5 wt. % TTDS (4,4′-DDS, 2,4′-DDS and TTDS totaling 0.39 mol),thereby giving 92 g of dried crystals. An HPLC analysis showed 17 wt. %4,4′-DDS, 83 wt. % 2,4′-DDS and 0.1 wt. % TTDS. A 5% acetone solutionthereof had an APHA value of 450.

Comparative Example 1

The procedure described in Example 1 was repeated except for reducingthe amount of 50% sulfuric acid so as to give a pH of 7.5. Seventy ninegrams of dried crystals were recovered, resulting in a 13 g decrease inyield compared with that of Example 1. An HPLC analysis showed 85 wt. %4,4′-DDS, 15 wt. % 2,4′-DDS and 0 wt. % TTDS. A 5% acetone solutionthereof had an APHA value of 200.

Comparative Example 2

The procedure described in Example 1 was repeated except for increasingthe amount of 50% sulfuric acid so as to give a pH of 4.0. Ninety eightgrams of dried crystals were recovered. An HPLC analysis showed 76 wt. %4,4′-DDS, 19 wt. % 2,4′-DDS and 5 wt. % TTDS. A 5% acetone solutionthereof had an APHA value of 1000. TTDS and coloring impurities weretherefore barely removed.

INDUSTRIAL APPLICABILITY

According to the process of the present invention, TTDS and coloringimpurities can be highly effectively removed using an aqueous solventwithout altering the isomeric composition of dihydroxydiphenylsulfone.Moreover, the process gives an excellent dihydroxydiphenylsulfonerecovery.

Furthermore, since organic solvents are not used, the process offersexcellent workability, safety, ecology and economy.

1. A process for producing dihydroxydiphenylsulfone comprising the stepsof: dissolving or suspending crude dihydroxydiphenylsulfone containingtrihydroxytriphenylsulfone in an aqueous solvent; adjusting the pH ofthe aqueous solvent to 5–7; optionally cooling the aqueous solvent; andseparating the precipitated crystalline dihydroxydiphenylsulfone.
 2. Aprocess for producing dihydroxydiphenylsulfone comprising the steps of:dissolving or suspending crude dihydroxydiphenylsulfone containingtrihydroxytriphenylsulfone in an aqueous solvent by adding alkali;adjusting the pH of the aqueous solvent to 5–7 by adding an acidicsubstance; optionally cooling the aqueous solvent; and separating theprecipitated crystalline dihydroxydiphenylsulfone.
 3. The process forproducing dihydroxydiphenylsulfone according to claim 1 or 2, whereinthe pH is adjusted to 6 or greater and less than
 7. 4. The process forproducing dihydroxydiphenylsulfone according to claims 1 or 2, whereinthe crude dihydroxydiphenylsulfone contains trihydroxytriphenylsulfonein a proportion of 30 wt. % or less.
 5. The process for producingdihydroxydiphenylsulfone according to claims 1 or 2, wherein thecrystalline dihydroxydiphenylsulfone is separated at 60° C. or lower. 6.The process for producing dihydroxydiphenylsulfone according to claim 3,wherein the crude dihydroxydiphenylsulfone containstrihydroxytriphenylsulfone in a proportion of 30 wt. % or less.
 7. Theprocess for producing dihydroxydiphenylsulfone according to claim 3,wherein the crystalline dihydroxydiphenylsulfone is separated at 60° C.or lower.
 8. The process for producing dihydroxydiphenylsulfoneaccording to claim 4, wherein the crystalline dihydroxydiphenylsulfoneis separated at 60° C. or lower.
 9. A method for producingdihydroxydiphenylsulfone comprising: dissolving or suspending crudedihydroxydiphenylsulfone containing trihydroxytriphenylsulfone in anaqueous solvent, said dihydroxydiphenylsulfone constituted of isomers;adjusting the pH of the aqueous solvent to 5–7 to precipitatecrystalline dihydroxydiphenylsulfone; and recovering the precipitatedcrystalline dihydroxydiphenylsulfon, wherein trihydroxytriphenylsulfoneand coloring impurities are separated therefrom without changing theproportion of the isomers.
 10. The method according to claim 9, whereinthe dissolving or suspending of the crude dihydroxydiphenylsulfone isaccomplished by adding alkali.
 11. The method according to claim 9,wherein the adjusting of the pH is accomplished by adding an acidicsubstance.
 12. The method according to claim 9, further comprisingcooling the aqueous solvent after the dissolving or suspending of thecrude dihydroxydiphenylsulfone.
 13. The method according to claim 9,wherein the pH is adjusted between 6 and
 7. 14. The method according toclaim 9, wherein the crude dihydroxydiphenylsulfone containstrihydroxytriphenylsulfone in a proportion of 30 wt. % or less.
 15. Themethod according to claim 9, wherein the crystallinedihydroxydiphenylsulfone is precipitated at room temperature to 90° C.16. The method according to claim 9, wherein the crystallinedihydroxydiphenylsulfone is recovered at 60° C. or lower.
 17. The methodaccording to claim 9, wherein the isomers are2,4′-dihydroxydiphenylsulfone (2,4′-DDS) and4,4′-dihydroxydiphenylsulfone (4,4′-DDS) wherein a weight ratio of2,4′-DDS/4,4′-DDS is 0.1/99.9 to 98/2.
 18. The method according to claim9, wherein the aqueous solvent is used 0.5–10 times the crudedihydroxydiphenylsulfone.
 19. The method according to claim 10, whereinthe alkali is an alkali metal hydroxide.